SOLVED Suggestions for extracting lines, and a couple of questions (Affinity Photo 2)

[nickbatz]

Hi, here's a zoomed-in screenshot showing part of a web of lines I'd like to extract and put against an alpha background for later use.

It's been paint-bucketed black in the top square, both are the same picture I'm playing with.

Suggestions for the easiest way to do that would be much appreciated.

***

Related questions: if I use Select Sampled Color and copy the selection from this pixel layer, why am I unable to paste just it onto a new pixel layer? Instead I'm getting even more of the aqua-colored waste area.

And hitting delete doesn't simply turn what's selected into alpha for some reason. Why?

(I'm using invert selection back and forth here, in case my question is confusing.)

Many thanks.

[nickbatz]

Okay, and here's the answer: use Select Sampled Color on the black, and then just copy/paste without creating a pixel layer first.

This is an example of the forum helping me figure something out even before anyone replied.

 

[firstdefence]

We aim to please, it's called quantum solving